Integrated backlight display system for a personal digital assistant
First Claim
1. A backlighting system for use in a personal digital assistant (PDA) of the type having a liquid crystal display (LCD) touch and display screen and providing an elongated interior space within the PDA to contain a stylus normally used for touching the display screen, comprising:
- a backlight driver circuit constructed on a printed circuit board (PCB) having a predetermined shape to fit within the elongated space normally occupied by the stylus; and
an electroluminescent film energized by the backlight driver circuit and adapted to be connected to the screen.
5 Assignments
0 Petitions
Accused Products
Abstract
A backlighting system is placed in an elongated interior space within a personal digital assistant (PDA) which normally houses a stylus used to touch a liquid crystal display (LCD) touch and display screen. A backlight driver circuit is constructed on a printed circuit board (PCB) which fits within the elongated space, and an on-off switch extends from the PCB to an exterior hole formed in the PDA housing. An on-time control turns off power to the backlight driver circuit after a predetermined time has elapsed following activation of the on-off switch, and a dimming control controls the amount of energy delivered to the electroluminescent film. A torroidal switching transformer of a high voltage power supply minimizes noise, and a switching controller switches adjustable width current pulses through the transformer to regulate the high voltage level. A flyback circuit captures and uses a portion of the back EMF energy created when the current pulses are switched through the switching transformer. A H bridge of transistors alternately connects the high voltage positively and negatively to energize the electroluminescent film.
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Citations
20 Claims
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1. A backlighting system for use in a personal digital assistant (PDA) of the type having a liquid crystal display (LCD) touch and display screen and providing an elongated interior space within the PDA to contain a stylus normally used for touching the display screen, comprising:
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a backlight driver circuit constructed on a printed circuit board (PCB) having a predetermined shape to fit within the elongated space normally occupied by the stylus; and an electroluminescent film energized by the backlight driver circuit and adapted to be connected to the screen. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A backlight driver circuit for energizing an electroluminescent film having conducting plates to develop backlight for a liquid crystal display (LCD) screen, comprising:
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a step-up torroidal switching transformer having a primary winding connected to a power source; a switching controller for switching current pulses through the primary winding of the switching transformer; a flyback circuit for capturing and storing a portion of a back EMF energy created when the current pulses are switched through the switching transformer, the flyback circuit including a flyback rectifier and a flyback storage capacitor connected to the primary winding to capture the energy from the back EMF and augment the energy from the power source by the back EMF captured; a high voltage rectifier and a high voltage storage capacitor connected to a secondary winding of the switching transformer to rectify and store a voltage created from the current pulses switched through the primary winding of the switching transformer, the voltage stored in the high voltage storage capacitor having a predetermined higher level than the voltage of the power source; and four transistor switch sections which connected to the high voltage storage capacitor and connected as a H bridge to the conducting plates of the electroluminescent film, each register switch section responding to switching signals applied thereto to connect alternately the predetermined high voltage positively and negatively with respect to the conducting plates of the electroluminescent film. - View Dependent Claims (18, 19, 20)
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Specification